Method and apparatus for flattening glass



, f Mmiionv AND; PPARATUS, FOR FLATTENING GLASS Filed oct. 1o 19,25'

W//Tf Patented Aug. 17, 1925.

,PATENT oFFlc-s.

SAMUEL A. MCKI'ITRICK, 0F SANDUSKY, OHIO.

METHOD AND APPARATUS FOR FLATTENING GLASS.

Application lcd G'ctober 10, 1925.

The present invention relates to improve ments in methods and apparatus for flattening curved shawls of glass either handblown or machine-blown, and has for its object to produce flattened shawls or sheets of glass which are as near perfectly flat as it is possible to get them. Y

The usual method of flattening such shawls of glass has been to place them upon fiat stones supported within a furnace on a carrier which is so mounted that the stone can be moved at intervals to different points within the furnace. The shawls are placed upon the stone while it is positioned at a point within the furnace where the temperature is sufficiently high to softenthe glass and cause it to lflatten out on the stone. The carrier is then moved to shift the stone to a point where the temperature is lower to permit the glass to cool and harden upon the stone. In this method, asheretoforepracticed, the glass lsheets produced have not been uniformly andV perfectly flat. The main reason for these 'imperfections was that the flattening' stones had been so supported on the carrier that they were not uniformly heated throughout which has resulted in the distortion of the top-surface of the stones by reason of unequal expansion, and this distortion of the surface of the stone causes a corresponding bow in the glass. By the method of the present inventionthe flattening stone Vis uniformly heated throughout so that its upper surface is not distorted which results in a much more perfect product.

It has been found, however, that the sheets have a tendency'to bulge slightly at the-center in cooling due to the fact that all portions of the sheet do not give off heat at the same rate and the contraction is not uniform throughout the entire sheet. The present invention has for an object to provide a method and apparatus by which the glass sheets are cooled upon the flattening stones in suoli manner that the sheets Yare caused to cool more uniformly and the slight bowing of the sheets due tothe unequal contraction thereof, is eliminated.

lith theabove objects in view the' inven-` tion may be said to comprise the method and v apparatus as illustrated in the accompanying drawingshereinafter described' and par-V ticularly set forth-in the appended claims together with 'such variations and modifications there@ 21S Will he apparent toene Serial No. 61,685.

present invention, flattening stones are supported on a movable carrier within the furnace in such a manner that the under surface of the stone as well as the top surface is exposed to the heating medium within the furnace so, that the stones are uniformly heated throughout and there will be no distortion of the flat top surface thereof by reason of unequal expansion and contraction. Portions of the furnace are heated to a higher temperature than others and the carrier uponrwhich the stones are mounted moved at intervals to shift the stones into and out of the hotter portion of the furnace. Each glass shawl to be flattened is placed upon a stone while the stone is inv the por- Jcion of the furnace maintained at a high temperature, the temperature at this point being such that the glass if softened and caused to be flattened upon the surface of the stone. The carrier is then moved to carry the stone with 'the flattening shawl thereon to a point where thetemperature is lower to permit the glass to cool and harden upon the flattening stone. In order to overcome the tendency of the glass sheet tobulge slightly inthe center, which may be due to a more rapid cooling of the under surface of the sheet which is in contact with the flattening stone than the upper surface thereof, the upper surface of the sheets of glass are subjected to the action of aV gaseous cooling medium which is directed upon the top surface of the sheets, compensating-for the more rapid cooling of the bottom Vsurface thereof so that the sheet remains-flat upon the stone while cooling'.y Y

VReferring tothe drawings, a glass flattening furnace which may be of the usual construction is indicated bythe numeral l and has located upon the interiorthereof a flattening'table 2,' the furnace being vconnected with theusual leer Structure Heat isili?,-

troduced .into the furnace yin any desired manner at the point indicated atrl in Fig. 1. Al number of flattening stones, in this instance four, are mounted `upon the table 2 and the movement of the table is such that each stone is positioned successively at the points indicated by the letters A, B, C and D in Fig. l of the drawings. The temperature of the point A is higher than at the points B, 'G and D, and the glassshawfls v6 are introduced through a passage 7 1and placed upon the stones 5 at therpoint A where the temperature -is such that theglass is softened and the shawls are flattened upon the stones. `The table 2 is turned tlv'irough a quarter *revolution at intervals such that the shawls will be permitted to be flattened 'on the sptonesvat the point A and to cool and harden'fwhile the stones occupy the posit-iene It has heretofore been the practice to place the vflattening stones upon'Y the 'flattening ywheeler table and then to briclr upl around the Vedges yof 'the stones until the stonesare encased fin Ylor-ick work. Thisbrickwvorlt extends up along the vedges ofthe flattening 'stnes to withii an inch or two of the top.

Y It has been foundthattlie top' surface of the Vstones 4mounted upon the' flattening table in the manner above describe-dV become Ymore or less 'curved or bowed on the top surface wliic'h' is undoubtedly due Vtoy theY 4fact' that theV flattening stones fareL not uniformly heatfe'd. The heat which impinges uponl the flattening stones heats the Aupper surfaces thereof toa niuchvgreater extent that any other portion ofthe stone and consequently the heat will cause the top of the stone to expand more than the lower part of the'stone and this will give the upper surfaces of the stones a curved or vbowed shape. Naturally the glass shawls which are flattened against the'Y stone having curve vorfbow in it wi-llhave the sainel curve or bow after the glass isY flattened against therstone and this curve or bow will persist inthe glass even Yafter the glass is vsent through the leer.

ln 'the present invention the, flattening stones 5 are so mounted uponl the flattening vwheel 2 that-thestones arel elevated above Y the flattening wheel and have the major por-A tiofn'iof thefbottom surface exposed to the heat of thefurnace. As rshownv herein the stones tirare supported upon spaced support' ingblocks S, a sufcientynumber of which are providedto adequately support the stone yet leave a sufficient space below' the sto-ne' for the heated gasses" to circulate, the height of thev flattening stone above the table 'being sufliienttoi'perinitthe ready circulay -t'ion'of het gases beneath the stone.`

' By? 'reason oftheconstruction above de scribed the'stonesTwillbe heatedby the cir-v cullat-in'ef the heated gases beneath the same wellas the heated gases impingedfupi on the --top surfaces thereof, and ,the heating effect onl the stones will be .approximately uniform so that the stones will expand or contract in .a -.-uniform manner. Therefore, ifunder suoli 'conditions a flattening stone has been given a satisfactory flat surface for insertion in the furnace, the top of the stone will remain 'flat dueto the fact that the equal heating will produce equal expansion and contraction throughout the -body of the stone.

lVhile vthe flattening stones may 'be kept flat 'by Ithe `means above-described, the sheets would nevertheless ibeliable to become slightvly distorted in cooling due to yununiform contraction caused by the more rapid cooling of the bottoni surface of the sheets, and the present invention aiinsto provide means for insuring uniform :cooling of the sheets of glass upon thecstones so that the glass sheets ywill cool and harden uponthe stones u ith all kportions thereof. remaining in -contact with the flattening surfaces of the stones.

To this end means is provided for causing currents of Vair cooler thanthe air `within the furnace. te in ipinge upon the top surface of the glass sheet while `it is in oiiefof the cooling positions vwithin the furnace, As shown yherein the cooling air is introduced through an air pipe 9 which communicates with a suitable source o f air underpressure and extends lthrough al wall'of the furnace. `With in the furnace the pipe 9 is provided with -a *T-shaped' discharge head 10 which is provided. with numerous small openings for the escape of air on the under side thereof rand which is so `positioned in the furnace that it is directly over the central portion of a glass plate or sheet when the flattening stone on which the sheet is placed is in one of the cooling positions. As shown herein the nozzle or head1() isrpositioned over the sheet'l carried by the flattening stone which is in the position B, The flow of air through the pipe 9 may be regulated by means ofl a suitable valve 11 to deliver the cooling air jets at a rate suitable'for" the desired'cooling effect. Y

Having described my invention, what I claim is:

l. The Lmethod of flattening curved shawls of rglass which comprisesplacing a shawl upon a flattening stone in a portion of'a y flattening furnace where theheat is sufficient to cause the glass to soften andfflatten out on "the stone, shifting said stone with the fiatllO stantially equal degree upon the top and bottom thereof to cause the glass to soften andl :flatten out Ion the stone, shifting the Stone to a point in the furnace Where `the temperature is lower, and applying a cooling medium to the top surface of the sheet of glass.

3. The method of flattening curved shawls of glass which comprises placing a shawl upon afiattening stone within a flattening furnace, applying heat to said stone to a substantially equal degree upon the top and bottom thereof to cause the glass to soften and flatten 'out on the stone, shifting the stone to apoint in the furnace where the temperature is lower, and directing a gaseous cooling medium upon the top surface of the glass sheet. l

4. A flatteningfurnace comprising an enclosing casing, a carrier within -the casing, a flattening stone supported on the carrier and movable to different positions in the furnace, and means associated with the furnace for directing a cooling medium upon a glass sheet resting on said stone.

5. A flattening furnace comprising an en! closing casing, a rotary carrier within the casing, a flattening stone supported on the carrier and movable to different portions of the furnace, and means associated with the furnace for directing a gaseous cooling medium upon a sheet of glass on said stone in one position thereof in the furnace,

In testimony whereof, I hereunto affix my signature.

SAMUEL A. MGKITTRICK. 

